In a conventional friction clutch for an automotive vehicle or similar application, a clutch disc having opposed friction faces adjacent the periphery is positioned between and driven by frictional engagement with a flywheel rotated by the vehicle engine and a pressure plate rotatably connected to and axially movable toward and away from the flywheel. The clutch disc is operatively connected to an input shaft leading to the vehicle transmission. A diaphragm or Belleville spring is utilized in the clutch assembly to urge the pressure plate towards the clutch disc and move the disc into engagement with the flywheel; the diaphragm spring generally being pivotally mounted on the cover for the clutch assembly.
Depending on the vehicle operator, a rapid release of the clutch pedal could result in a sudden grabbing or engagement of the disengaged clutch disc by the rotating pressure plate and flywheel resulting in a sudden shock to the clutch disc. This sudden engagement does not provide a smooth ride for the vehicle and seriously reduces the effective life of the clutch, whether of the rigid or progressive type.
To avoid the grabbing action and resulting shock to the clutch disc, a cushioning arrangement is necessary to obtain a desired smooth clutch engagement providing a steady and progressive action from the initial point of clutch engagement to the point when all slip ceases with a positive clutch engagement. Early efforts to provide this cushioning effect included a series of small springs riveted between the friction facings of the clutch disc to bias the facings axially outwardly. Other versions have involved an elongated cushioning spring mounted in the fulcrum edge on the pressure plate. The present invention provides an improved means to obtain modulation of engagement of the friction elements of the clutch.